1. Field of the Invention
The present invention relates to an aqueous ink for ink jet recording which is suitable for use in an ink jet recording apparatus, particularly an ink jet recording apparatus of a bubble jet system, and which provides ejection stability and high head durability, and to an ink jet recording method using the ink.
2. Related Background Art
The ink jet recording method carries out recording by ejecting ink droplets to attach them onto a recording medium such as paper. Specifically, an ink jet recording method disclosed in JP-B-S61-59911, JP-B-S61-59912, and JP-B-S61-59914, i.e., a bubble jet recording method uses an electrothermal converter as ejection energy supply means to give thermal energy to an ink in order to generate a bubble in the ink, which bubble pushes out an ink droplet. This bubble ink jet method allows a recording head to have multiple orifices at a high density, enabling recording of a high-resolution and high-definition image at a high speed.
In the above bubble jet recording method, as the temperature of a heater provided in a nozzle is instantaneously raised to 300° C. or higher (to be said as 360° C.), ink components or thermally decomposed product thereof and impurities (hereinafter referred to as “koga”) may deposit on the surface of the heater. Since such deposit impairs heat conduction from the heater to the ink, foaming in the ink may not occur properly, resulting in printing defect. The deposition of a substance derived from the ink components on the surface of the heater is called “kogation” and is an obstruction to the improvement of the durability of a bubble jet type ejection head.
Since above koga is mainly derived from organic substances, kogation may occur in both dye ink and pigment ink. Various studies have been previously made to improve this phenomenon. In particular, in an ink including a water-dispersible pigment, koga tend to be produced in large quantities to deposit on the heater, or durability of the head tends to deteriorate. Meanwhile, as low running cost is desired for an ink jet recording apparatus more and more, a head having higher durability is demanded.